Question

$\text{If twice the zero of the polynomial}\text{p(x) = 2x - 4 is equal to zero of the}\text{polynomial q(x) = 5x + a, then what}\text{is the value of a ?}$

• A. 20
• B. -20
• C. 10
• D. -10

Answer 1

The correct option is B -20

$\text{To find the zero of a polynomial}$,
$\text{we equate the polynomial to zero.}$
$p\left(x\right)=0\Rightarrow$ $2x-4=0$
$\Rightarrow$ $x=2$
$\therefore \text{2 is the zero of the polynomial}p\left(x\right)=2x-4.$
$\text{Given that the zero of the polynomial}q\left(x\right)=5x+a\text{is twice the zero of}\text{the polynomial}p\left(x\right).$
$\Rightarrow \text{The zero of the polynomial}q\left(x\right)\text{is 4}$
$\Rightarrow q\left(4\right)=0$
$\Rightarrow 5\left(4\right)+a=0$
$\Rightarrow a=-20$